Tafsiran Ulangan 28:13: Ramban, Ibn Ezra, Tur HaArokh & Rav Hirsch

AND THE ETERNAL WILL MAKE THEE THE HEAD, AND NOT THE TAIL. The meaning thereof is that He will make you the head of all peoples and not the tail of any one of the nations, for it is possible that you will be the head of many peoples and yet be the tail of one nation more distinguished than you. The correct interpretation is that He will henceforth make you the head and at no time will you ever be the tail. Similarly, thou shalt be above only⁸⁴In Verse 13 before us. always, and thou shalt not be beneath⁸⁴In Verse 13 before us. forever.

if you will hearken i.e., if you will resolve in your heart to observe and to practice. The core principle is not to depart from following God , and thereby engage in idolatry; for idolatry — i.e., the denial of God — is the root of all transgressions. Conversely, to affirm the unity of God is to observe and to practice the commandments, in the sense that it is the root of all observance and of all practice.

לראש ולא לזנב, “as a head and not as a tail.” As a head of all the nations, and not as a tail of a nation more distinguished than you. It was possible, theoretically to rank as number one overall among the nations, and at the same time to trail some nation in a specific matter. Alternately, Moses might have meant that in a best case scenario, when you deserve it, you will be the number one among all the nations, but in a worst case scenario, even when you have endured chastisements by G’d, you will never be the tail, i.e. the lowest ranking of all the other nations.